Objective:
1. Assess and parameterize for models, the effects of changing temperature, vapor pressure, atmospheric carbon dioxide and ozone on crop performance. (Booker, Fiscus, Burkey)
1.A. Design and construct an air exclusion system for treating crops with elevated ozone, elevated temperature and elevated atmospheric carbon dioxide concentrations.
1.B. Assess and parameterize for crop growth models (DSSAT-CSM -CROPGRO-Soybean and DSSAT-CSM-CERES-Wheat), the effects of elevated ozone, temperature and carbon dioxide on soybean and wheat physiology, above and belowground growth and development, yield and seed quality.
1.C. Characterize interactive effects of temperature, vapor pressure, carbon dioxide and ozone on plant growth in outdoor controlled environment systems.
2. Characterize the effects of the major climate change variables temperature, atmospheric vapor pressure, carbon dioxide, ozone and possible interactions on the infection rates and progression of the disease in plants infected with wheat rust. (Fiscus)
3. Identify soybean germplasm that will contribute to development of stress tolerant cultivars. (Burkey, Booker)
3.A. Identify soybean cultivars with enhanced ozone tolerance.
3.B. Characterize the inheritance of ozone tolerance in soybean ancestors.
4. Identify the mechanisms through which soil microorganisms mediate perennial grasses, forage legumes and ecosystem responses to changing climate conditions. Develop economically sustainable production systems for forage and biomass crops that reduce the net emissions of greenhouse gases per unit of forage or biomass production. The research will contribute to the ARS GRACEnet project.

Approach:
Experiments will be conducted in available open top field chambers, greenhouse exposure chambers, and custom Outdoor Plant Environment Chambers (OPECs) or in a new air exclusion system to be developed by this project that allow for testing of plant responses to combinations of carbon dioxide and ozone under contrasting conditions of temperature and vapor pressure deficit. A multi-year field study will be established using the air exclusion system to test the effects of elevated ozone, temperature and carbon dioxide on a soybean-winter wheat continuous no-till cropping system. Detailed assessments of plant growth, biomass, and yield along with measurements of leaf gas exchange, tissue chemistry and micrometeorological data will be used as inputs for parameterization of DSSAT-CSM CROPGRO-Soybean and CERES-Wheat models. Ozone-sensitive and tolerant snap beans will be grown in the OPECs where control of relative humidity and temperature allows for the study of plant responses to elevated ozone and carbon dioxide under contrasting vapor pressure deficit conditions. Wheat cultivars that are susceptible and resistant to stripe or stem rust will be grown in the OPECs and inoculated with pathogens under a range of carbon dioxide, ozone, temperature and vapor pressure deficit conditions to examine the potential impact of these climate change factors on infection and progression of disease. Soybean germplasm will be exposed to elevated ozone conditions in greenhouse exposure chambers or open-top field chambers and foliar injury and seed yield measurements used to identify tolerant cultivars. Single nucleotide polymorphism markers will be applied to a soybean population developed from a cross between ozone-sensitive and tolerant soybean ancestors and the population screened for ozone-induced foliar injury in the greenhouse. Marker and phenotype data will be combined to develop a map of soybean ozone-tolerance genes.